I think I found the solution on Raymarine's support site. Thanks Porkchunker.
Question
I am not able see any C-MAP NT+ chart detail on my Pathfinder series chartplotter display. The world map disappears at a certain level, and then all I am left with is a white screen with some cross-hatch lines, and the words NO CHART DATA. What is the problem?
Answer
The Pathfinder series of chartplotters, chart/radar, and chart/sonar displays have a feature in them called PLOTTER MODE. Plotter Mode is a feature that allows you to zoom the chartplotter through it's full range of available chart scales, without having to have a map cartridge inserted. This is most frequently used on occasions where you might be in an area for which you do not have a map cartridge. Plotter Mode allows you to zoom in tight on your plotted waypoints and route line even though there is no map data available.
Another possible use of Plotter Mode is for precision navigation drills such as anchoring, finding a precise dive spot/wreck, or performing search and rescue type maneuvers. With plotter mode enabled, most Pathfinder series chartplotters can zoom in to a range of 1/64 nautical mile. This gives you a very "magnified" view of a waypoint to allow you to precisely position your boat on or near it.
For normal day-to-day navigation Plotter Mode should normally be turned off. this restricts the chartplotter to only those range scales that actually are present on the C-MAP NT+ electronic chart cartridge. In highly detailed areas you may be able to range into 1/32 or 1/64 NM range scale. In less detailed areas, the maximum zoom may be restricted to 3, 6, or 12 miles (such as in open-ocean areas.) If you find that the system is not allowing you a close enough view of your plotted track or waypoint, simply enabling Plotter Mode will allow you to zoom closer, however, the map detail will be switched off. This is to prevent a condition called OVERZOOM, where the map data is over magnified, and stretched to fit a scale it was not intended for. This condition could cause serious distortion and inaccuracy of the electronic chart, hence the reason the chart itself disappears when Plotter Mode is enabled, and an unsupported range is selected.
Plotter Mode is enabled or disabled as follows:
Press the MENU key.
Select the CHART SETUP soft key.
Scroll down to PLOTTER MODE in the chart setup menu.
Select the OFF or ON soft key to enable or disable the setting.
Press the CLEAR key 3 times to exit the menu system, and return to normal operation.